


Cobalt

by 43501



Category: Undertale (Video Game)
Genre: Other
Language: English
Status: Completed
Published: 2015-09-27
Updated: 2015-09-27
Packaged: 2018-04-23 13:41:44
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,561
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4878991
Author URL: https://archiveofourown.org/users/43501/pseuds/43501
Summary: <blockquote class="userstuff">
              <p>Several weeks have passed since you fell into these labyrinthine subterranean caverns. It's time for you to move forward. [Explicit Sans x Reader, the reader insert's sex is undefined and can be interpreted as either male or female.]</p>
            </blockquote>





	Cobalt

Moments slowly tick by.

Observing your surroundings for the umpteenth time during your long wait, your glance scans the horizon of Sans’ bedroom from the vantage point of his bed. Nearby, a flashlight haphazardly taped into a lamp illuminates the area. Trash is scattered about on the floor and a disused treadmill stands as the ironic centerpiece of the slobbish bedroom. You stare at the door again, clutching handfuls of creased bedsheets in your frustration.

You put forth your most valiant effort not to think about the gargantuan mound of dirty, mismatched socks in the corner of the room. You especially try not to think about how you could’ve sworn you’ve seen the pile move on its own accord. For what it was worth, Sans was at least polite enough to make his bed for you to sit on when you told him you needed to speak with him.

You startle when the door swings open and Sans steps into the room, toting a bottle of ketchup. He pushes the door shut with his shoulder as he kicks off his slippers one after the other, aiming them onto sock mountain.

“Hey there.”

“hey.” Approaching, Sans closes a fist around the ketchup bottle, squirting half of its contents into his mouth. Trying not to stare too openly, you glance at his teeth, then at his neck where there was no apparent esophagus. You stopped trying to figure out the mechanics of monsters long ago.

“oh, sorry. how impolite of me. want some?” The skeleton holds the condiment in your direction, offering it up.

“I’m, uh... I’m good. I’m still full from eating at Grillby’s earlier.” You lie, doing your best not to wince.

“suit yourself. more for me later.” He clicks the cap closed on the tortured, half-bent ketchup bottle and tosses it carelessly onto the floor before joining you on the bed, sitting by your side.

He stuffs his hands into his pockets and tilts his head sharply, cracking the bones in his neck. “let me guess, you’ve finally decided to go?”

He hadn’t even allowed you the space to begin the conversation. The fact that he immediately cut to the heart of the matter throws you off guard, but on a moment’s reflection, it was just his style.

“That’s right. I’ve been thinking, and I’ve decided I need to press onward to the capital in the morning. I can’t stay here forever.” The word ‘morning’ draws out from you differently than the rest of your speech -- deep in the caverns and far from the sun, monsters had a rather tenuous concept of the passage of days.

The queer orbs of light floating in his otherwise hollow eye-sockets slowly shift sideways, avoiding meeting your gaze. “you do what you gotta do, kid. i knew you’d decide to leave sooner or later. been seeing it in your eyes for a while.”

“Don’t misunderstand. It’s nothing to do with you, or with anyone else here.” You quickly interject. “You and your brother have shown me a lot of hospitality.”

“yeah, yeah. i’m not misunderstanding you. every other human who’s fallen down here came to the same conclusion eventually.”

At the mention of the others before you, your fingertips instinctively gravitate to your pocket, feeling for the contents. A silky hair ribbon, picked up on your travels. The sudden gravity of the situation weighs down on your consciousness and makes you fearful.

“don’t sweat it. trust me, asgore can be reasoned with. if there’s anyone that can do it, it’s you.” Apparently sensing your unease, Sans slings an arm around your shoulders, squeezing you into an assuring half-hug. You should be used to this sort of contact by now - you’ve been living under his roof for a couple of weeks - but your throat closes and your cheeks burn hot nevertheless.

“It’s not that simple. That’s not the only thing on my mind.”

“oh? then hows about you start from the top.”

You finally return the partial hug, scooting over to close the gap between Sans and yourself. You sigh and tilt your head back, rubbing at your eyes, thinking where to start.

***

Frankly, you’re not sure how you got yourself into this situation. About an hour ago you were waiting anxiously in Sans’ room, consumed with concern. You spoke of your multitudinous fears: the others before you, the journey to the capital, that mysterious shape-shifting flower slinking in the shadows, tracking your movements.

Conversation eventually lapsed into silence. Silence lapsed into something else entirely, you and Sans playing at one another in idleness as you’d done countless times before in private, curious and exploratory. You realize that the stagnant air of the room and the close smell of his bones ought to repulse you. Instead, you find a strange comfort and familiarity in it. 

You offer no resistance and question nothing as he seizes your waistband, drawing your pants down to your knees, rending your legs bare. You cooperate and wriggle the rest of the way out of your garments, kicking them to the floor.

Wordlessly, the skeleton braces his hands on your lower back and pulls you toward him, his guidance authoritative yet affectionate. The springs of the beaten-up mattress beneath you groan as you shift your weight in perfect tandem, until Sans is flat on his back, head on his pillow, with you straddling his bony hips.

Smooth skeletal hands abandon their post against your back and tenderly traverse the outside of your bare thighs. An inexplicable shiver crawls down your spine when his skinless phalanges close on you, his hard fingers digging down deep into your soft flesh.

“not bad.” He comments casually, despite shamelessly regarding your exposed lower half. His permanently-fixed grin stands out in your mind more than ever when you strain through the darkness to peer down at him.

You squirm in response to both his open leering and his fleshless hipbones jutting unforgivingly into you. His pants are thin and do nothing to offer you cushioning.

“So... how does... this work, exactly?” You manage to stagger out, tentatively running the heel of your palm over his crotch, finding nothing there but his pelvis.

“oh, don’t worry. i’ll be sure to throw you a bone.” The skeleton gives you a broad wink. “don’t be so impatient. there’s no need to rush. we’ve got all night, don’t we?”

Before you can muster a response, his right hand strays to pry at the space between your legs. There is no warmth to his touch as the tip of his digit teases at your opening, setting the nerves there alight. His other hand remains gripping you by the knee, commanding you to stay in place.

“W-wait, Sans, perhaps-”

“don’t worry.” He replies. His voice is gentle in an attempt at being reassuring, but it’s also clear that he has no intention of allowing you to back out now. “i’ll show you a good time.”

His probing fingers become more insistent, more hungry. Your body accepts this and seems to relax. A single phalange of his slides easily past your entrance. You keenly feel every bone and joint as he sinks himself knuckle-deep.

Taken with him for the moment, you bend forward deeply to plant a gentle kiss on his cheekbone. You can feel him working a second finger into you, pistoning long, deep strokes between your legs. Though not quite able to kiss you back, his eye sockets half-shut in obvious contentment at the gesture. Your face is close enough to feel his gusting breath, heavy and hot. In this moment, it’s exceptionally intimate.

You take a deep breath and right yourself, parting from him with some reluctance. He withdraws himself from you and rubs his hands together, concentrating on something. You recognize this behavior as him focusing his magic.

“welp, that’s enough foreplay. time for the main event. watch this.”

With a sharp snap of his fingers, a ghostly cock materializes from his crotch in a brilliant flourish of blue-hued magic. Cool blue light creates a unique ambiance and floods the room around you, emanating from the palms of his hands and his summoned appendage. It stands erect and tangible against your front, despite its ethereal appearance.

“Don’t even say it.” You warn him, sensing what was coming. Your hand instinctively curls around the curious object, appreciating its girth.

“aw. and here i thought you’d find it... humerus.”

You feel like heaving a sigh of exasperation, but Sans gives you a quick, good-natured squeeze and a wink as a stand-in for an apology before hoisting you up.

With his hands guiding you by the hips, you lower yourself onto him, taking his length into you inch-by-inch. You elicit a pleased sigh from him when you meet his base, the fullness of him inside you palpable and satisfying. You draw upward and fall back onto him, setting up an easy rhythm.

He lazily halfway bucks his hips into you with every other stroke, mostly using his strong hands to bounce you on his lap, save for the occasional particularly impassioned thrust. You brace yourself on him and do your best to pick up his slack, riding him out long and slow, the bizarrely smooth, slick texture of his phantasmal cock gliding pleasantly against your inner walls.

Shadows cast from his still-glowing hands dance about the room as you move together, bodies melding. You chance a look down at him, your fingers closing around his rib bones where your hands are braced. Bathed in the light of his own magic, the bones of his skinless face gleam, the protrusion of his cheeks and the deep hollowness of where his eyes should be more pronounced than usual, mouth still firmly set into that wide smile. Then, without warning, he fondly touches your abdomen, focusing his soul energy into you.

Something akin to an icy wind courses through your veins and bursts in your chest when it hits your heart. A strange pressure behind your eyes causes the world to flash shades of blue for a moment. You try to blink it away, but your visage contorts reflexively into an expression of pain at the horrible familiarity of the sensation from battles past.

But, when Sans abruptly shoves you down onto his conjured member, the feeling that washes over you is so dizzingly pleasurable it renders you speechless. You now keenly feel every slight shift of his body against you as though it were the most tantalizing, orgasmic thing ever. Your chest tightens, your pulse quickens. You lose sight of everything else. Your jaw goes slack as the skeleton working under you becomes the center of your cobalt world, spearing you over and over, grasping, skeletal hands leaving deep, bony imprints in your flesh.

You clamp down on him, skin burning, chest heaving. Your eyes squeeze shut and your head rolls back, on the precipice of your own climax.

Nothing happens.

He’s ceased moving and is holding you in place. You collect yourself enough to blink down at him, incredulous and bewildered. He doesn’t give you any time to process the turn of events and forces himself upright, the motion toppling you onto your back, allowing him to mount you.

Sans is unexpectedly heavy. The sudden weight of his frame bearing down on you squeezes the breath out of your lungs. He is heedless when he presses his hard-edged body against yours, encircling you in his arms, trapping you between him and the bed as he pumps his hips into you.

You grit your teeth and shift within the tight confines, going cheek-to-cheek with him. You reach up to complete the embrace, feeling the gaps in his ribs against your forearms. Your hips flex needfully up into his, pleading for the full length of his shaft.

Plunging himself mercilessly into your warm depths, his ministrations are rough and wanton. You quiver and writhe perceptibly beneath him, your legs floating up to wrap themselves around his hips and force him as deep into you as he could manage.

You’re cognizant of the sounds your combined movements create: the rustling of his relaxed plastic-textured jacket, the slap of your skin against his bones, the squelching where you were joined, the frenzied creaking of the mattress springs that Papyrus next door was sure to notice. The fact that Sans appears utterly unconcerned with this is somehow very arousing.

Your eyes fly wide open when a spark of magical energy quickly crawls over the surface of your skin. There’s a startling bulging in your interior. You squirm, body straining to accommodate to the sudden marked swell of Sans’ member inside you.

“g-growing pains, huh.” He manages to grunt huskily in your ear, punctuated with another sharp thrust, the words catching in his throat.

You try to say something in response, but another brisk push of him against you makes you choke. You’re trembling. Sensing your peak for the second time, Sans delivers a few final, deliberate thrusts, finally wrenching the ecstatic cries free from your throat as your white-hot pleasure boils over.

You remain joined for several moments after, catching your breath. Your pubis feels tender, like it’s bruising from slamming against him.

You twitch when he picks himself up, drawing out from you. In the limited light, you notice your fluids staining the pants that he hadn’t bothered to remove.

Tracing your line of sight, his shoulders roll in a shrug. “it’s not a big deal. i’ll take care of it later.”

“Yeah. Sorry.” You reply inanely, cheeks burning.

“no prob.”

With a second snap of his fingers, the phallic apparition and energy from his hands snuff out like a candle in a breeze, plunging the room into almost-total darkness once more.

While your mind is racing, sounds and the shifting of the bed make you aware that Sans is settling beside you. His bones click as he shuffles about to make himself comfortable, synthetic jacket crinkling. An extended silence passes between you.

The realizations that were blocked out by your spontaneous lovemaking pour over you the longer you stare at the darkened ceiling, unfettered by distraction now. This may be the last time you stay in this house. This may be one of the last times you share alone with Sans. Your chest aches powerfully when you feel your shoulder pressed against his and you realize you don’t particularly want to be anywhere else. It seems too important not to comment upon, but you’re also not sure what to say.

“Hey, Sans?”

You want to say something, but his breathing is already deep and steady, softly whistling past teeth.

***

You stand at the edge of Snowdin, having said your farewells. The cozy village that embraced you with open arms stands at your back. In front, the permafrost plateaus blanketed in pristine snow stretch out eastward into the distance, running alongside clear rivers. The sight of it all fills you with determination.

The crunching of footsteps on snow alerts you to the presence of someone approaching. You turn to face them and are surprised to find Sans at a standstill, hands buried deep in his pockets, his familiar smile tugging inexplicably at your heartstrings.

When he speaks, he says something you don’t fully comprehend, but for some reason, you feel like you should.

“it was good to have you again. come back to this timeline sometime, yeah?”


End file.
